1970 Structural Steel Grade
1970 Structural Steel Grade
(OP)
Hello All,
Wondering what your opinion is on the grade of structural steel in 1970 Construction. We are doing some work on a 280 ft steel truss above a sports arena. We are not doing much in terms of loading so testing is out of the question. I do however have to check some elements for incidental loading.
The plans do not state grades, but the members are 12WF16 and 12WF27. Would the grades be equivalent to todays A992 or would it be more like A36?
I have one member that fails by 1% when fully loaded with a conservative load (100psf on a limited access walkway) so by judgment i'd say it is adequate... I can use load reduction factors but I am curious what you all think.
Wondering what your opinion is on the grade of structural steel in 1970 Construction. We are doing some work on a 280 ft steel truss above a sports arena. We are not doing much in terms of loading so testing is out of the question. I do however have to check some elements for incidental loading.
The plans do not state grades, but the members are 12WF16 and 12WF27. Would the grades be equivalent to todays A992 or would it be more like A36?
I have one member that fails by 1% when fully loaded with a conservative load (100psf on a limited access walkway) so by judgment i'd say it is adequate... I can use load reduction factors but I am curious what you all think.






RE: 1970 Structural Steel Grade
1% on one member is not significant. My opinion only.
RE: 1970 Structural Steel Grade
RE: 1970 Structural Steel Grade
I would explain to the owner that 36 ksi steel usually has a yield point near 48 to 50 ksi, so the 1% is strictly a calculated value, not a real reflection of the building strength. If they're still worried, they should test it.
RE: 1970 Structural Steel Grade
Unless you have other information from drawings, calculations, or lab testing of the steel, I would conservatively material.
If your results are consistently over by a large amount, I would consider testing the critical members.
Mike McCann
MMC Engineering
RE: 1970 Structural Steel Grade
RE: 1970 Structural Steel Grade
Sorry...
Mike McCann
MMC Engineering
RE: 1970 Structural Steel Grade
A thought: if they do not realize that a 1% overage into the considerable safety factor on one member out of many, with conservative assumptions, is insignificant perhaps they shouldn't be requesting calculations in the first place, since they are obviously unable to grasp their significance. I know we can't control our clients but honestly, some bureaucrats out there just want to check things off their to-do list with no thought as to reality, it would seem. But why would they ask to see them if you can't understand them anyway? (Rhetorical question, of course.)
RE: 1970 Structural Steel Grade
BA
RE: 1970 Structural Steel Grade
When I started working in the late 70's the use of 50ksi steel was the exception not the rule; no one wanted to spend the extra $.05/lb.
RE: 1970 Structural Steel Grade
Are you submitting calculations in STAAD, or a similar software package, perhaps? If so then I understand the dilemma: the failure of one member, even by a small margin, fails the whole system. And it's not good for repeat business to submit calculations that say "FAILURE" on them. Is that the case? If so there are probably some means to address that.
RE: 1970 Structural Steel Grade
I am not using STAAD as it is not that complex. I am however using software to run most of my beam clacs and the member in question does state FAILS on it. the entity that reviews calcs means well but they are not engineers, they are Building Code Officials (the special ones are Master Building Code Officials :) ). They flagged me once for not showing a calc of a 5" weld that was only loaded with 1kip shear... so i know they actually follow the loads but don't have enough sense to understand it all. I once had to teach them about modes of failures for beams and lateral bracing.
And we are trying to get more business with them so submitting failures never looks good as you mentioned. And to muddy the waters, the reviewer is the client and the owner of the existing building, just different departments.
I plan on just adding notes onto the calcs stating why the overage is deemed acceptable.
RE: 1970 Structural Steel Grade
RE: 1970 Structural Steel Grade
RE: 1970 Structural Steel Grade
Dik